1. Field of the Invention
The present invention relates to a technique for holding a semiconductor wafer by a vacuum chuck.
2. Description of Related Art
In a manufacturing process of a semiconductor device, a vacuum chuck is used for holding a semiconductor wafer.
FIG. 1 shows a part of a semiconductor manufacturing process using a vacuum chuck. A semiconductor wafer is mounted on a wafer cassette (step S1). A transit mechanism takes out the semiconductor wafer from the wafer cassette, and passes it to a CMP (Chemical Mechanical Polishing) apparatus (step S2). The semiconductor wafer is attached to a polishing head of the CMP apparatus. The semiconductor wafer is polished with a CMP process (step S3). The transit mechanism receives the semiconductor wafer treated with the CMP process, and conveys it to a washing apparatus (step S4). The washing apparatus washes the semiconductor wafer (step S5). The washed and dried semiconductor wafer is returned to the wafer cassette (step S6).
FIG. 2 is an example of the side view of the transit mechanism for conveying the semiconductor wafer in steps S2 and S4. A transit mechanism 107 includes a supporting unit 108, a vacuum system 114, an air supply system 116, and a switching valve 118. An upper surface of the supporting unit 108 is a flat sucking surface 110 for supporting the semiconductor wafer 2 horizontally. Wafer sucking openings 112 are formed on the sucking surface 110. The wafer sucking openings 112 connect to the vacuum system 114 and the air supply system 116 via the switching valve 118.
FIG. 3 shows an example of the arrangement of the wafer sucking openings 112 as the sucking surface is seen from above. The wafer sucking openings 112 are formed in appropriate positions suitable for sucking the semiconductor wafer 2.
At step S2, the semiconductor wafer 2 is taken out from the wafer cassette, and is placed on the sucking surface 110. The vacuum system 114 implements vacuuming for the wafer sucking openings. The semiconductor wafer 2 is held by the vacuum chuck.
The transit mechanism 107 moves the semiconductor wafer 2 held on the sucking surface 110 to the CMP apparatus. The polishing head of the CMP apparatus is lowered or the transit mechanism is lifted and a wafer underside surface 6 contacts to a polishing head. The polishing head sucks the semiconductor wafer 2 in vacuum, and conveys the semiconductor wafer 2 onto the polishing table.
Slurry is supplied and flowed on a rotating polishing pad and the polishing head pushes the surface for manufacturing devices (wafer front surface 4) of the semiconductor wafer 2 to the polishing pad with rotating. After the polishing process of a predetermined amount is completed, the semiconductor wafer 2 is sucked in vacuum and fixed to the polishing head, and released from the polishing pad. The polishing head holding the semiconductor wafer 2 moves to a place over the transit mechanism 107. The polishing head is lowered or the transit mechanism is lifted and the wafer surface 4 of the semiconductor wafer 2 contacts to the sucking surface 110 of the transit mechanism 107. The polishing head releases the semiconductor wafer 2. Similar to step S2, the transit mechanism 107 holds the semiconductor wafer 2 by the vacuum chuck.
When a conveying robot holds the semiconductor wafer 2 and the transit mechanism 107 releases it from the vacuum suction, the semiconductor wafer 2 is passed to the conveying robot. The conveying robot returns the semiconductor wafer 2 to the wafer cassette. When the washing apparatus is installed in the system, the semiconductor wafer 2 is returned to the wafer cassette after conveyed to the washing apparatus to be washed.
Depending on the manufacturing system, the polishing process may be implemented on a plurality of the polishing tables in order to improve process performance of the apparatus. When the polishing is implemented on the plurality of the polishing tables, the semiconductor wafer 2 is returned to the transit mechanism from the polishing head, and is treated by another polishing head via another transit mechanism.
In Japanese Laid-Open Patent Application JP-A-Heisei 07-302832, an example of a vacuum suction apparatus is described. In this Patent Application, a vacuum suction apparatus for preventing working fluid to flow between the vacuum sucking surface and the underside surface of a specimen is disclosed.